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Hi Paul,
ZTF show it as of yesterday at 13.6 g, 13.1 r
https://alerce.online/object/ZTF25abbgajqCheers
RobinA comparison of the current spectrum with one in the low state March 2024
https://britastro.org/observations/observation.php?id=20250810_221150_5f858c960a245997Cheers
RobinSo no detectable gas. (The positioning of the label in fig 2 indicating the band where CN should appear is unfortunate. At a casual glance it looks like the hot pixel there is a signal. Given that they took 6 spectra it is surprising they did not remove them)
Proper motion confuses the heck out of some of the bots auto reporting transients. They compare the sky with their library image, looking at the differences and once the proper motion moves the star out of the psf of the library image it suddenly triggers a bright transient ! There are quite a few examples in the Transient Name Server
If you look at the image cutout at SIMBAD
https://simbad.cds.unistra.fr/simbad/sim-basic?Ident=ZZ+PSc&submit=SIMBAD+search
and blink between the DDS and SDSS images you can actually see the position move between the two survey dates. The J2000 position is between the two (Sometimes for high proper motions you even see a double image Red/Blue in the colour DSS images because of the difference in dates)An ApJL preprint on ArXiv today presents events for the probable direct imaging of a lower mass companion of Betelgeuse:
There’s an excellent episode from the BBC World Service “Science in Action” programme on this
https://www.bbc.co.uk/programmes/w3ct6yfm“Have we found Betelgeuse’s ‘Betelbuddy?’ An astronomical mystery seems to be solved as the long-predicted stellar companion to the bright star Betelgeuse has been detected by a team of researchers led by Steve Howell of the NASA Ames Research Center using the Gemini North telescope in Hawaii. Steve discusses this breakthrough alongside astronomer Andrea Dupree of the Harvard Smithsonian Center for Astrophysics, who has discussed the predictions of this star on previous Science in Action programmes.”
Here is some further information from Alexander on the spectroscopy side which I have been asked to also distribute to the wider spectroscopy community. It is similar monitoring to that requested by Paul Roche which covered mainly 2018-2021 and was reported on the ARAS and BAA forums
https://www.spectro-aras.com/forum/viewtopic.php?t=2128
https://britastro.org/forums/topic/request-for-monitoring-of-x-per————————————————————————————-
Call for Spectroscopic and Photometric Monitoring of X Persei (4U 0352+309)Observers are invited to join a monitoring campaign on the Be/X‑ray binary X Persei, which is currently in an unusually low X‑ray state.
The campaign is coordinated by Alexander Salganik, PhD researcher at the University of Turku, Finland, whose work focuses on the Swift/BAT X‑ray light curve of the system. Since 2001 X Persei has shown three major X‑ray outbursts roughly every seven years. The next expected outburst has not occurred, and the source now sits at its lowest X‑ray flux in more than twenty years. Optical monitoring will help determine the current state and physical properties of the Be star’s disk, including whether it remains present or has dissipated during this faint phase.
Spectroscopy: priority is high‑resolution Hα (6563 Å). Additional coverage of He I 6678 Å, He I 5876 Å, or Hβ 4861 Å is welcome. Target cadence is one observation per week.
Photometry: UBVRI is very welcome. If limited, R and V bands are most useful, with R particularly sensitive to disk emission.
Data can be sent directly to Alexander Salganik (alsalganik “at”gmail.com), who will provide regular feedback and campaign updates.
The paper is now in A&A and a press release from University of Warwick
(At one point there was a possibility of me appearing on BBC Midlands Today but it was pushed off the list by other events !)
Cheers
RobinI am not sure if the transmission grating (grism) used in the direct vision spectrograph you are using is sensitive to polarisation though.
Transmission gratings are not sensitive to polarisation so that is one thing less to worry about 😉
https://www.edmundoptics.co.uk/f/transmission-gratings/13496
Cheers
RobinOne thing you could do without having to calibrate is to compare the spectrum of the antitwilight sky with that in different directions. Just divide the two spectra to see the difference (Adjust the exposure so the intensity is similar to reduce problems with non-linearity of the camera and be sure to switch off any automatic colour correction in the camera).
Note though that some reflective gratings respond differently depending on the polarisation which changes depending on the direction in the sky. This is an example of the response of a reflection grating. S and P are for the two directions of polarisation. You can also see why you need to consider the grating response as well as the camera QE if you want an absolute flux calibration
https://www.optometrics.com/assets/M466Sales.pngI am not sure if the transmission grating (grism) used in the direct vision spectrograph you are using is sensitive to polarisation though. This shows typical curves for some transmission gratings but it does not show any effect of polarisation.
https://www.optometrics.com/assets/ARTx.png
The one in your spectrograph will probably be similar to the 600l/mm curveCheers
RobinYou can approximately calibrate the spectrograph in relative flux using a tungsten lamp of known temperature which will have a black body curve but this will not include the effect of the atmosphere. If you then measure the sun at two different elevations you can then also estimate the effect of the atmosphere. You will need to calibrate the spectrum in wavelength first though
Cheers
RobinNote that even if you know the QE of the camera, this is not enough to flux calibrate the spectrum as there are many other effects between the sun and the camera sensor. The atmosphere and the grating efficiency are the main ones. You need a known light source to flux calibrate spectra. For astronomical spectroscopy this is done by measuring a star with a known spectrum as described in my document here
http://www.threehillsobservatory.co.uk/astro/Relative_flux_calibration_20221222.pdf
but that would not be straightforward with your setup.Can you describe in more detail what you are trying to measure about the solar spectrum ?
Cheers
RobinThe only caveat with these high reflectivity dielectric mirror coatings is that the reflectivity can plummet outside the visible range, particularly into the UV below 4000A. Something to keep in mind if doing spectroscopy at that end of the spectrum.
Only 10 Lyrids on my NW facing camera last night 21/22nd, though cloud was patchy and completely clouded over by 02:00 UT so probably missed the peak
I just thought it was suspicious to get 3 meteors so close together and parallel within a 30 second period.
Specular reflectance flares from satellite constellations perhaps ?
Cheers
RobinIf it is gas from an eruption it will be interesting to see if it turns into a dark (absorption) feature in UV images once it reaches the sunlit area
Robin
European institutions including British will need to step up to fill some of these gaps.
There are other important resources like this in Europe like CDS (SIMBAD etc) for example, and others which form a global “astro-ecosystem”. This is less to do with money and more to do with politics and cultural shifts in the US though of course.
The controlled constant temperature that cooling provides also means that calibration frames can be re-used
Robin
Interesting graphics from NASA in this article. The accretion disc appears to be around the wrong star, with the erupting T CrB occuring in the outer regions of the disc. Wow!
I did a reverse image search and tracked it back to where it was repurposed from in 2010
https://svs.gsfc.nasa.gov/20184
not that it makes it any better but at least we now know who was to blame !They actually do also have a decent animation linked from that page showing the accreting system but not the outburst
https://svs.gsfc.nasa.gov/20393/EDIT the explosion is shown in a further animations down the page
I see at least Space.com put a question mark at the end of their headline and quoted Jeremy’s scepticism (Also the lack of any evidence in the RV data to support the presence of a suggested third body to trigger the outburst on certain dates.)
https://www.space.com/the-universe/stars/hold-onto-your-hats-is-the-blaze-star-t-corona-borealis-about-to-go-boom
